A long straight cylindrical region of radius a curries a current along its length. The current density (J) varies from the axis to the edge of the cylindrical region according to `J = J_(0) ( 1 – r / a)` Where r is distance from the axis `(0 lt r lta)`
(a) Find the mean current density.
(b) Plot the variation of magnetic field (B) with distance r from the axis of the cylinder for `0 lt r lt a`.

Answer

`J_(0)/3` (b)`(##IJA_PHY_V02_C10_E01_031_A01##)`